Spliced joint in coated web material and method of forming said joint



Sept. 29, 1970 R. T. BOURNS ETAL 3,531,362

SPLICED JOINT IN COATED WEB MATERIAL AND METHOD OF FORMING SAID JOINTFiled Oct. 30, 1967 n W//"// m 6' Z/ lk 0 /2 Fla 2 LAW/FENCE G. M DONALDR/CHA/PD 7'. BOURNS.

. 4 ATTOR/V rs United States Patent Office 3,531,362 SPLICED JOINT INCOATED WEB MATERIAL AND METHOD OF FORMING SAID JOINT Richard T. Bournsand Lawrence G. McDonald, Rochester, N.Y., assignors to Eastman KodakCompany, Rochester, N.Y., a corporation of New Jersey Filed Oct. 30,1967, Ser. No. 679,083 Int. Cl. B32b 3/06 US. Cl. 161-39 Claims ABSTRACTOF THE DISCLOSURE A method for reducing coating disturbances at splicesin a web being coated by treating the trailing edge of the splicing tapeand the adjacent web surface with a material to prevent air entrainmentin the coating.

Background of the invention In many manufacturing operations asubstantially continuous web is coated with a liquid material, such asaqueous solutions or dispersions of hydrophilic colloids, see US. Pats.2,681,294 and 2,739,891, which may then be dried to form the desiredproduct. Such manufacturing processes are used in the manufacture ofadhesive tapes, magnetic recording tapes and photographic films andpapers, among others. In order to increase the efficiency, andconsequently lower the cost, of manufacturing these products, thecoating process generally is carried out in a substantially continuousmanner. Inasmuch as the web or support for the coating can only beobtained in finite lengths, a new supply roll of the web must beperiodically spliced to the end of the preceding supply roll so that thecoating process may continue uninterruptedly.

It has been found that the most desirable way of splicing such webs isto utilize a splice tape extending across the web and joining the twoadjacent pieces of the web together. It has also been found thatapplying the splice tape to the surface being coated provides fewercoating flaws than does the application of the splice tape to the backside of the web. However, even though the application of the splice tapeto the coated side of the web results in fewer coating problems than doother methods of splicing, streaks and other defects have still beenfound in the coating downstream from the splice tape. Normally, thespliced section of the continuous web is cut from the finished productand is scrapped so that the defects in the coating occurring at thesplice joint are not found in the final product. However, it has beenfound that under certain conditions, the splice joint may affectsubstantial lengths of the coated web following the splice. In manyproducts, it is possible to cut out the affected portion of the webwithout substantially affecting the usability of adjacent portions.However, in many products this is not possible, and the entire webcontaining such defects must be scrapped.

As the speed of coating webs is increased and as the width of the webproducts is also increased, the value of the product being scrapped dueto splice-imparted defects downstream from the splice have becomeexcessive. This is even more true in high-cost products utilizing anexpensive coating material which cannot be easily recovered fromscrapped portions of the web. As a result, it has become increasinglyimportant to minimize, it not eliminate, defects resulting from thesplice from the coated web products. Moreover, the elimination of thesedefects must be accomplished without materially increasing the cost ofthe product.

Furthermore, the elimination of the splice-imposed defects must not inany way result in other, potentially less desirable defects in thecoated product. Additionally,

3,531,362 Patented Sept. 29, 1970 the method of eliminating thesplice-imposed defects must be readily accomplished without affectingthe production rates now possible in high-speed coating machines.

Summary of the invention Accordingly, the present invention provides amethod of treating a splice joint in a web to be coated, whereby thesplice does not cause coating defects downstream of the spliced joint.

Many of the defects in coated webs appear to result from the entrainmentof air in the coating deposited on the web or from the adherence of asmall bubble of air to the coating nozzle, which then affects furtherportions of the coating deposited on the web. It has been found thatsuch entrained air is picked up and such bubbles are generated as thecoating drops down over the splice tape onto the surface of the web. Theair being entrained appears to come from that trapped in the angleformed between the edge of the tape and the surface of the web.

Accordingly, the present invention provides a method of continuouslycoating a moving web with a layer of a substantially liquid materialcomprising the steps of moving the web past a coating head anddepositing a layer of a substantially liquid material on a surface ofthe web. At spaced longitudinal intervals, a splicing member or tape isapplied to the surface of the web being coated, with the splicing memberforming a discontinuity in the web surface, at least at the downstreamedge of the splicing member. Defects in the web coating aresubstantially reduced by preventing the entrainment of air from thedownstream edge of the splice member.

More specifically, the elimination of air entrainment from thedownstream edge of the spliced member is provided by coating thedownstream edge of the splice membet and the adjacent web surface withan oily hydrophobic coating such as the marking solution from a felttipped marker.

Additionaly, the prevention of entrainment of air from the downstreamedge of the spliced member may be provided by feathering the downstreamedge of the splice member.

Also, the elimination of air entrainment may be provided by coating thedownstream edge of the splice member and the adjacent web surface with acoating of rubber cement.

The various features of novelty which characterize the present inventionare pointed out with particularity in the claims annexed to and forminga part of this specification. For a better understanding of theinvention, its operating advantages and the specific objects obtained byits use, reference should be had to the accompanying drawings anddescriptive matter in which the preferred embodiments of the presentinvention are illustrated and described.

Brief description of the drawings FIG. 1 is a greatly enlarged schematicsection through a spliced joint of a coated web which may be treated inaccordance with the teachings of the present invention; and

FIG. 2 is a greatly enlarged schematic section through a spliced jointtreated in accordance with an alternative method of the presentinvention.

Description of the preferred embodiment A sectional view through a websplice is illustrated in -FIG. 1, wherein the trailing end of one Web 10is spliced to the leading end of a succeeding web 12 by a strip ofsplicing tape 14 which extends across the joint therebetween. In thisillustration, the web moves past the coating station in the direction ofarrow 16. The layer or coating 18 of a substantially liquid material,such as aqueous solutions (which term is also intended to includedispersions) of hydrophilic colloids and, more specifically, agelatin-silver halide emulsion, is deposited at the coating section. Itwill be seen that the splice tape 14 creates a discontinuity in thesurface of the web at both the leading and the trailing edges. It hasbeen found that, as the spliced joint of the web moves past the coatingstation, the layer of substantially liquid material generally followsthe discontinuous surface at the leading edge of the splice tape.However, a wedge of air 20 is trapped in the trailing edge of the splicetape and the coated layer does not closely follow the surface of the webat that point, especially at high coating speeds. The wedge of air 20trapped between the coating material, the surface of the web, and thetrailing edge of the splice tape has been found to become entrained inthe liquid coating material as the coating material settles to thesurface of the web. The entrained air may then be spread over thesucceeding downstream portions of the web, causing defects in thecoating which may result in rejection of the final product. Moreseriously, some of the trapped air 20 may form small bubbles whichadhere to the surface of the coating nozzle and affect the stream ofmaterial flowing therethrough. These bubbles may persist for an extendedlength of time whereby all succeeding coating is affected. As a result,the amount of defective webs may be substantially greater than would beexpected due to entrapment of air in the coating alone.

One method of preventing the entrainment of air in the subsequentlycoated web is illustrated in FIG. 2 (wherein similar reference numbersrefer to similar elements) in which the trailing edge of the splice tape14' is feathered or beveled so that no discontinuity is formed betweenthe trailing edge thereof and the adjacent web surface. As a result ofthis treatment, no air is present at the trailing edge of the tape whichmay be entrained in the coating or which may adhere to the coatingnozzle.

Another method of preventing the entrainment of air from the splicejoint in the coating is to treat the trailing edge of the splice tapeand the adjacent web surface with a filler material such as rubbercement, which performs substantially the same function as the featherededge of the tape; i.e., filling the transition from the tape to the Websurface to eliminate the wedge of air at the trailing edge of the splicetape.

More surprising, however, is the discovery that air entrainment-causedcoating defects may be substantially eliminated by coating the trailingedge of the splice tape and the adjacent web surface with a materialwhich is not wet by the coating liquid and letting the volatile solventsevaporate before coating the web. In the coating of a water-basedcoating material, it has been found that superior results are obtainedby simply marking the trailing edge of the splice tape and the adjacentweb surface with a felt-tipped marking pen. As disclosed in US. Pat.2,676,349, such marking pens have a marking ink which is comprised of ahighly volatile carrier containing a pigment of finely divided solids.It has been found that one such marking solution carrier has a solventcomposed substantially of aromatic hydrocarbons, predominately xylenes,and high flash naphtha. Apparently, this treatment prevents theimmediate wetting of the trailing edge of the splice and the adjacentweb surface by the coating material so that the coating materialactually bridges the air wedge without permitting air to be entrained inthe coating material or to form bubbles which may adhere to the coatingnozzle as may occur when the coating material is immediately attractedto the web surface. More particularly, treatment of the trailing edge ofthe splice tape and the adjacent web surface with the solution from aMarks-A-Lot felt-tipped marking pen provided extremely satisfactoryresults.

It has also been found that an oily-hydrophobic material, such as asolution of oil in methyl-ethyl-ketone, also provides very satisfactoryresults.

Another material which has also been successful is a high flash napthafraction containing a non-volatile fraction of oily material which alsorenders the web and tape surface non-wettable by the coating material.

While applying the treating coating to the web surface immediatelyadjacent the trailing edge of the splice tape, as by treating the webbefore applying the splice tape, provides satisfactory results, moredesirable results are obtained by coating both the trailing edge of thesplice tape and the surface of the web thereadjacent. At the same time,it has been found that merely coating the trailing edge of the splicetape alone does not eliminate the defects in the subsequent coating.

Accordingly, in the process of continuously coating the surface of amoving web with a substantially liquid material, the web is transverselyspliced at spaced longitudinal intervals, resulting in a discontinuityin the surface being coated. The present invention prevents theformation of disturbances in the coating downstream from the spliceddiscontinuity by preventing entrainment of air in the coating, either byeliminating the Wedge of air at the downstream edge of the splice, or bythe application of an oily-hydroprobic material to the splicediscontinuity.

In extremely high speed coating operations it may be desirable to alsotreat similarly the leading edge of the splice tape.

An additional benefit of the preferred embodiment of the presentinvention; i.e., coating the splice with a marking pen, is the fact thatthe treated splice is readily apparent due to the color of the markingsolution, so that any failure to treat the splice joint is readilyapparent.

In addition, while the foregoing discussion has been directed to theformation of splices using a splice tape, the present splice treatmentmay be successfully applied to other types of splice joints such as lapjoints between the two ends of the web.

We claim:

1. In the continuous coating of a moving web with a layer of an aqueoussolution of hydrophilic colloids, the method of eliminating disturbancesin the layer of said aqueous solution downstream from a spliced joint inthe web comprising the step of preventing said aqueous solution fromentraining air from the spliced joint by coating the web surfaceimmediately downstream from the spliced joint with a hydrophobic oilprior to applying the layer of aqueous solution.

2. The invention according to claim 1 wherein the substantiallyhydrophobic oil is the marking solution from a felt-tipped marker.

3. The invention according to claim 1 wherein the spliced joint isformed with a splicing tape on the web surface to be coated.

4. In the continuous coating of a moving web with a layer of an aqueoussolution of hydrophilic colloids, the method of eliminating disturbancesin the layer of said aqueous solution downstream from a spliced jointformed with a splicing tape on the web surface to be coated comprisingthe step of forming a tapered transition from the downstream edge of thesplicing tape surface to the web surface.

5. The invention according to claim 4 wherein the downstream edge of thesplicing tape is feathered to the surface of the web.

6. The invention according to claim 4 wherein the transition is filledwith an oily-hydrophobic material.

7. The invention according to claim 4 wherein the transition is filledwith rubber cement.

8. The invention according to claim 1 wherein the hydrophobic oilconsists essentially of a solution of oil in methyl-ethyl-ketone.

9. The method of coating a layer of an aqueous solution of hydrophiliccolloids on a moving web comprising the steps of applying a splicingmember to the surface of the web to be coated, said splicing memberforming a discontinuity in the web surface at least at the downstreamedge of said member, applying a hydrophobic oil material to thedownstream edge of said member and the web surface adjacent thereto, andthen moving the web and the splicing member past a coating head anddepositing the layer on the web.

10. A web product having a splicing member applied to one surface of theweb, said splicing member forming a discontinuity in the web surface onthe downstream edge of the splicing member, said discontinuity and thesurface of the web adjacent to and downstream of the discontinuityhaving a coat of an oily-hydrophobic material, and a coating layer of anaqueous solution of hydrophilic colloids disposed on said one surface ofsaid web and said oily-hydrophobic material.

References Cited UNITED STATES PATENTS PHILIP DIER, Primary Examiner US.Cl. X.R.

